FIELD OF INVENTION
Slitter machines of the prior art are designed to complete the packing process on filled tab lock corrugated cases. The machine's in-line design initially slits the tab-locks on filled corrugated cases, positions the loose flaps for sealing, and seals the flaps with a series of hot glue guns. The case is then sealed and discharged on a compression conveyer. Many of the machines of the prior art are designed to accommodate cases of varying size and as such are quite complex.
An in-line slitting machine of the prior art is discussed in U.S. Pat. No. 4,551,964 (the '964 patent), commonly assigned to applicant and incorporated herein by reference, which eliminates the need to turn the case. The machine of the '964 patent applies pressure to the sides of the case, and exposes the tab-locks for cutting.
Filled corrugated cases are fed into the slitter portion of a slitter machine. The cases are directed into the machine, held down by rollers, and indexed onto an infeed lug chain. The rollers hold the case down, ensuring it does not jump the leading lug on the infeed lug chain. The leading lug serves as the infeed timer and controls the entry of cases into the machine.
The infeed chain then separates the cases and directs them toward the main flight chain, using rubber side-drive chains. The side-drive chains grip the case horizontally, controlling it as it advances toward the main flight chain. The side drive chain runs at the same speed as the main flight. The main flight chain includes flight lugs which lift the leading edge of the case and twist it. The case is twisted to expose the front and rear tabs to a pair slitter knife guides. The slitter knife guides incorporate a sharpened edge along their upper portion functioning as a knife. As the case passes through the knife guides, the tab locks are cut. Once through the slitter, the end flaps are then raised by an end flap lifter and directed through a flap tucker which closes the front and rear flaps, leaving the side flaps in a down position.
Once the case has passed through the flap tucker, the side flaps are lifted by flap guides. These guides ensure that the side flaps are lifted up and away from the side of the case as it exits the slitter section. This step is accomplished to avoid any binding of the flaps. As the case moves out of the slitter section, it is indexed onto a conveyor belt at the infeed of the sealer section. The case then enters a set of flap guides, which control the position of the flaps as they enter the glue applicator.
Once the case has entered the glue section, the side flaps remain upright until the glue is applied to the inside of the flap. The case is then directed forward into a compression section, which closes the two side flaps using flap guides and seals the case using a series of rollers. The cases are then discharged from the machine onto the customer's discharge conveyor.
The infeed timer uses wedge-shaped steel lugs mounted to a pair of timing chains perpendicular to product flow to ensure that the cases enter the slitter at the rate of movement of the flight chain. The lugs are moveably positioned at a distance less than the desired case length apart along the chains. The timing chains are mounted between two side-drive chains such that a case is accelerated forward against a first lug and is raised up on top of a second following lug. When the first lug passes the end of the infeed timer, the case is accelerated downstream by the side drive chains. The timer is mechanically synchronized to release one case into the slitter in time with the main flight chain, located downstream. The pair of side-drive chains operate at the same speed as the main flight chain, and have two sections of rubber lugs that propel the cases forward against the timer lugs. One problem with the timer of the prior art is the time and accuracy required to effect a changeover for a different case size. The lugs must be mechanically removed from the timing chains, a sample case positioned on the conveyor and the lugs must be repositioned for the newly desired case length. Frequent case size changeovers cause problems with lug and fastener wear, chain stretch, drive sprocket alignment and wear, leading to timing problems between the infeed section and the warping section of the machine. Another problem with the prior art is that the case may be dropped into the flight chain too early either because the side drive chain is not properly positioned or the side drive chain width is set too wide. These problems are caused by the fact that physical movement of separate elements to effectuate case size changes are required, including case width adjustment of the drive chains and advance or retard of the side drive chain.
The main flight chain transports the cases from the timer through the slitter guides, end flap lifters, and the flap tucker section. After directing the cases through these sections, the flight chain then discharges the cases from the slitter to the transfer conveyor. The flight chain is made up of two flat-top chains having, for example, 12 sets of leading and trailing flight lugs, attached thereto. The main flight chains ride on plastic tracks for minimal noise and friction. Each set of flight lugs carries and controls one case. The leading edge of a case rests on a set of leading flight lugs and is prevented from sliding off by the associated trailing flight lug. The leading flight lugs are fixed along the main flight chains at an interval less than the smallest desired case length. The trailing flight lugs are mechanically moveably connected to the main flight chains to allow positioning of the trailing flight lug further from, or closer to, the preceding flight lug to accommodate a full range of case lengths in, for example, six 1.5 inch increments. A stationary cam is located near each chain having a profile to contact the flight lugs such that the cases are lifted and twisted as they advance along the flight chain. A problem with the prior art transport chain is the time required to make a case size changeover. In order to effect a changeover, all 12 sets of lugs must be removed from the chains and reinstalled at the proper position. Frequent changeovers also lead to wear of the lugs and fastening elements. In addition, the flight chains of the prior art are relatively long and the weight of the lugs causes the chains to stretch which leads to wear, alignment and timing problems.
The tab lock slitter guides of the prior art mount two spring-loaded blades vertically on either side of the main flight chain. As the flight lugs advance up their respective cams, lifting and twisting the case, the front and rear tab-locks are exposed to the blades. The knife guides are wedged into the gaps created between the case and its side flaps as the case proceeds along the chain. As the flight lugs ride down their respective cams, the case is forced down onto the knives, thus cutting the tab-locks. Each case is held in place by a case hold-down, which is suspended from a side of the machine frame and positioned above the case. One problem with tab lock slitters of the prior art is their limited ability to accommodate the deviation in position of the tab locations. If the tabs of a certain case are too high for instance, the knife will fail to completely slit the tab causing a machine jam. An additional problem with tab lock slitters of the prior art is that there exists a limited amount of accuracy available in accommodating different case sizes. For instance, case centering is changed by physically loosening both sets of knife guides placing a case on the main flight chain and moving the guides within a prescribed distance from the case while ensuring parallelism of the guides. Improper adjustment of the guides can result in erratic tab lock slitting. The integral knife guide/blades of the prior art also pose a problem of edge sharpening and blade replacement. In order to effect a blade change or to sharpen the knife edges the guides must be remove from the machine causing delays and down time.
The end flap lifters of the prior art consist of a pair of flat-top chains, mounted vertically on both sides of the main flight chain. Teardrop shaped lugs, controlled by cams on inclined frames, lift both the front and rear flaps as a case advances downstream. The teardrop on the right side of the machine lifts the leading case flap, while the teardrop on the left side lifts the trailing case flap. The chains also transport wedge-shaped lugs which prevent the side case flaps from springing outward as the case passes between the teardrops.
The flap tucker of the prior art is a slotted, rotating disc, followed by a horizontal plow, located at the discharge end of the slitter. Just as the leading flap is pushed to a vertical position by the teardrops, it strikes the flap tucker and is folded downward into the case. As the trailing flap is pushed to a vertical position by the teardrops, it enters the slot in the flap tucker and is forced down. The case is then passed through a plow, which holds the front and rear flaps down as it exits the slitter and enters the sealer. Problems resulting from improper case changeover adjustment or wear include timing problems where the tear drops lifting the cases or the flaps not lifting, or where the tear drop width adjustment is incorrect causing centering problems. The tear drop assemblies of the prior art comprise a cantilevered mounting arrangement which contributes to wear and alignment problems.
As described hereinabove, slitter machines of the prior art function to accommodate tab lock cases of various sizes. In order to accommodate the diverse case sizes mechanical adjustment of numerous elements of the machine is required. Starting with the infeed section, a case of new dimension is placed in the infeed roller position and the infeed roller adjustment bolts are loosened to position the roller within a prescribed distance above the case and then retightened. The infeed rollers are then manually centered over the edge of the case by loosening a pair of adjustment handles. The width of the side-drive chain must next be adjusted by loosening several hold down bolts on the pair of side-chain drive units, placing several filled cases of product between the units, manually adjusting the space between the units within a prescribed distance from the cases and equidistant from the centerline of the machine, then retightening the hold down bolts.
Next, the case pocket length must be adjusted to accommodate the new case length. A case is placed on the main flight chain between a leading and a trailing flight lug and the trailing lugs are removed and repositioned to within a prescribed distance from the case and reattached ensuring that the pairs of trailing lugs are parallel. The machine must be jogged forward until all 12 sets of lugs have been adjusted to the correct pocket length. The knife guides must next be adjusted to accommodate a new case height or width. The width of the knife guides are adjusted by placing a case in the pocket moving the guides within a prescribed distance from the case ensuring that the guides are equidistant from the centerline of the machine. The height of the knife guide is adjusted by loosening a pair of locks which hold the knives in place and then manually moving the knife guide to within a prescribed distance of the tab lock on the leading end of the case and then the locks are re-engaged.
The case flap guide must also be adjusted during a case size change and is effected by positioning a case first in the infeed timer section and then in the main flight chain and loosening a plurality of mounting bolts and manually raising the guides such that the flaps are retained within the guides and that the guides are within a prescribed distance from the sides of the case and are equidistant from the centerline of the machine.
Next the rear flap lifters must be adjusted to accommodate a case change. The front flap lifters are timed with the leading end of a case and the flap tucker and therefore do not require adjustment during changeover. To adjust the rear flap lifter adjustment, bolts on the drive shafts are loosened and the shafts are manually turned to position the flap lifter in proper orientation with the case. The case guides are also adjusted to accommodate a width change on a case by placing a case within the guides and loosening the hold down bolts on the pair of case guides and positioning the guides within a prescribed distance from the case and equidistant from the centerline of the machine, then the hold down bolts are retightened. The flap lifter width is adjusted similar to the case guides to accommodate a case width change ensuring that the flap lifters are equidistant and parallel to the centerline of the machine. Next the height of the flap tucker must be adjusted to accommodate each case height change. The flap tucker is adjusted by loosening an adjustment handle and placing a case under the flap tucker and manually positioning the flap tucker within a prescribed distance from the case. The timing of the flap tucker must also be adjusted to accept a new case size and it is effected by loosening the bolts that attach the flap tucker to its drive shaft, placing a case on the flight chain and jogging the machine to position the case under the tucker locating the vertical flap into the disc cutout with a prescribed clearance. The bolts are retightened and the machine jogged to ensure the proper adjustment.
What is needed is a slitter machine which can accommodate frequent case size changes with a minimum amount of time, expertise and effort, without requiring the use of tools, and without the deleterious effects on the life of the machine parts.